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CVE-2019-25375· NVD / CVE Program· CNA VulnCheck

OPNsense 19.1 Reflected XSS via monit interface

OPNsense 19.1 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject malicious scripts by submitting crafted input to the mailserver parameter. Attackers can send POST requests to the monit interface with JavaScript payloads in the mailserver parameter to execute arbitrary code in users' browsers.

MediumCVSS 5.1 · v4.0—No exploit No fix recorded
Published
Feb 15, 2026
Updated
Jun 16, 2026
EPSS
0.4% · 30th percentile
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Action score

20

Monitor

Low priority for now.

CVSS
20 / 40 · 5.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · VulnCheck
5.1
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.

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Affected systems

VendorProduct
opnsenseopnsense

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • opnsense opnsense19.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (VulnCheck). Independent of NVD's CPE analysis and usually ahead of it.

  • Opnsense OPNsense

    • 19.1affected

Same product

opnsense: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-39008A command injection vulnerability in the component /api/cron/settings/setJob/ of OPNsense Community Edition before 23.7 and Business Edition
    40Plan
  • CVE-2023-39001A command injection vulnerability in the component diag_backup.php of OPNsense Community Edition before 23.7 and Business Edition before 23.
    40Plan
  • CVE-2025-50989OPNsense before 25.1.8 contains an authenticated command injection vulnerability in its Bridge Interface Edit endpoint (interfaces_bridge_ed
    39Monitor
  • CVE-2023-27152DECISO OPNsense 23.1 does not impose rate limits for authentication, allowing attackers to perform a brute-force attack to bypass authentica
    39Monitor
  • CVE-2023-39007/ui/cron/item/open in the Cron component of OPNsense Community Edition before 23.7 and Business Edition before 23.4.2 allows XSS via openAct
    39Monitor
  • CVE-2023-39004Insecure permissions in the configuration directory (/conf/) of OPNsense Community Edition before 23.7 and Business Edition before 23.4.2 al
    39Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2019-253690 days apartOPNsense 19.1 Stored XSS via system_advanced_sysctl.php
    20Monitor
  • CVE-2019-253700 days apartOPNsense 19.1 Reflected XSS via interfaces_vlan_edit.php
    20Monitor
  • CVE-2019-253710 days apartOPNsense 19.1 Reflected XSS via diag_ping.php
    20Monitor
  • CVE-2019-253720 days apartOPNsense 19.1 Reflected XSS via diag_traceroute.php
    20Monitor
  • CVE-2019-253740 days apartOPNsense 19.1 Reflected XSS via vpn_ipsec_settings.php
    20Monitor
  • CVE-2019-253760 days apartOPNsense 19.1 Reflected XSS via proxy endpoint
    20Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
A
Scope
X

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records